1. Field of the Invention
The present invention relates generally to a dimpled lifting pipe for mining deep-sea mineral resources, and, more particularly, to a lifting pipe which is used in a manganese nodule mining system including a collection device for collecting deep-sea manganese nodules and a lifting pump and which has a structure in which dimples are formed on the surface of the lifting pipe so as to reduce drag so that the lifting pipe is less influenced by flows of ocean current.
2. Description of the Related Art
Due to an increase in the global demand for mineral resources, marine mineral resources are attracting attention as new alternatives. Of these marine mineral resources, deep-sea manganese nodules have flat or spherical shapes, are blackish brown and are non-crystalline. They are soft when they are collected, and they are easy to break when they are dry.
Such manganese nodules are chiefly composed of manganese, iron, silicic acid and moisture. The quantities of ingredients vary depending on location. There are two theories for the formation of manganese nodules: the theory that manganese nodules were precipitated from colloidal hydroxides and the theory that manganese nodules were precipitated due to the catalytic reaction of ion oxide. Manganese nodules are present in the deep sea (4000˜5000 m in depth), and grow about 0.01˜1 mm every 1000 years.
As shown in FIG. 14, a system 10 for mining such deep-sea manganese nodules includes a collection device 12 to be disposed on the bottom of the deep sea, a lifting pipe, a lifting pump 14 system, a buffer, and a mining ship 16 to be located on the sea surface. Manganese nodules are separated and collected from the bottom of the deep sea by a collection device, the concentration of the flow of the manganese nodules is optimized in the buffer below the lifting pipe, that is, in an intermediate storage space, and then the manganese nodules are continuously transferred to the top of the sea through the lifting pipe.
However, prior art lifting pipes have lengths ranging from hundreds of meters to a thousand meters and have circular cross-sections. Accordingly, these prior art lifting pipes vibrate due to ocean currents of the deep sea and such vibrations make stable mining using collection devices and lifting pumps difficult due to the vibrations of the lifting pipes and cause technical difficulties to the entire lifting system. Accordingly, a reduction in drag upon these lifting pipes can be an important solution to the alleviation of the above problem.